diff --git a/Lib/test/string_tests.py b/Lib/test/string_tests.py
index cd3ee48a92..ae1254945d 100644
--- a/Lib/test/string_tests.py
+++ b/Lib/test/string_tests.py
@@ -1237,6 +1237,14 @@ class MixinStrUnicodeUserStringTest:
                          (PY_SSIZE_T_MAX + 1, ''))
         self.checkraises(OverflowError, '%.*f', '__mod__',
                          (INT_MAX + 1, 1. / 7))
+
+        self.checkraises(OverflowError, '%c', '__mod__', -1 << 1000)
+        self.checkraises(OverflowError, '%c', '__mod__', -1)
+        self.checkequal('c=\x00', 'c=%c', '__mod__', 0)
+        self.checkequal('c=\U0010ffff', 'c=%c', '__mod__', 0x10ffff)
+        self.checkraises(OverflowError, '%c', '__mod__', 0x110000)
+        self.checkraises(OverflowError, '%c', '__mod__', 1 << 1000)
+
         # Issue 15989
         self.checkraises(OverflowError, '%*s', '__mod__',
                          (SIZE_MAX + 1, ''))
diff --git a/Lib/test/test_long.py b/Lib/test/test_long.py
index fd15f04ace..aca5aaaba0 100644
--- a/Lib/test/test_long.py
+++ b/Lib/test/test_long.py
@@ -712,6 +712,14 @@ class LongTest(unittest.TestCase):
                 self.assertEqual(format(value, format_spec),
                                  format(float(value), format_spec))
 
+        # test 'c' specifier limits
+        self.assertRaises(OverflowError, format, -1 << 1000, 'c')
+        self.assertRaises(OverflowError, format, -1, 'c')
+        self.assertEqual(format(0, 'c'), '\x00')
+        self.assertEqual(format(0x10ffff, 'c'), '\U0010ffff')
+        self.assertRaises(OverflowError, format, 0x110000, 'c')
+        self.assertRaises(OverflowError, format, 1 << 1000, 'c')
+
     def test_nan_inf(self):
         self.assertRaises(OverflowError, int, float('inf'))
         self.assertRaises(OverflowError, int, float('-inf'))
diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 503a59e1ef..12228fd572 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -14373,6 +14373,7 @@ wrongtype:
 static Py_UCS4
 formatchar(PyObject *v)
 {
+    int overflow;
     /* presume that the buffer is at least 3 characters long */
     if (PyUnicode_Check(v)) {
         if (PyUnicode_GET_LENGTH(v) == 1) {
@@ -14389,16 +14390,17 @@ formatchar(PyObject *v)
             if (iobj == NULL) {
                 goto onError;
             }
-            x = PyLong_AsLong(iobj);
+            x = PyLong_AsLongAndOverflow(iobj, &overflow);
             Py_DECREF(iobj);
         }
         else {
-            x = PyLong_AsLong(v);
+            x = PyLong_AsLongAndOverflow(v, &overflow);
         }
-        if (x == -1 && PyErr_Occurred())
-            goto onError;
+        /* either PyLong_Check(v) or PyLong_Check(iobj) is true, so it is
+           guaranteed that no error occurred in PyLong_AsLongAndOverflow. */
+        assert(!(x == -1 && PyErr_Occurred()));
 
-        if (x < 0 || x > MAX_UNICODE) {
+        if (overflow || x < 0 || x > MAX_UNICODE) {
             PyErr_SetString(PyExc_OverflowError,
                             "%c arg not in range(0x110000)");
             return (Py_UCS4) -1;
diff --git a/Python/formatter_unicode.c b/Python/formatter_unicode.c
index a2c2b3627c..f20d077e14 100644
--- a/Python/formatter_unicode.c
+++ b/Python/formatter_unicode.c
@@ -860,6 +860,7 @@ format_long_internal(PyObject *value, const InternalFormatSpec *format,
     Py_ssize_t prefix = 0;
     NumberFieldWidths spec;
     long x;
+    int overflow;
 
     /* Locale settings, either from the actual locale or
        from a hard-code pseudo-locale */
@@ -889,12 +890,12 @@ format_long_internal(PyObject *value, const InternalFormatSpec *format,
             goto done;
         }
 
-        /* taken from unicodeobject.c formatchar() */
         /* Integer input truncated to a character */
-        x = PyLong_AsLong(value);
-        if (x == -1 && PyErr_Occurred())
+        x = PyLong_AsLongAndOverflow(value, &overflow);
+        if (x == -1 && PyErr_Occurred()) {
             goto done;
-        if (x < 0 || x > 0x10ffff) {
+        }
+        if (overflow || x < 0 || x > 0x10ffff) {
             PyErr_SetString(PyExc_OverflowError,
                             "%c arg not in range(0x110000)");
             goto done;